Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems.
3GPP Long-term evolution (LTE) complements the success of High Speed Packet Access (HSPA) with higher peak data rates, lower latency and an enhanced broadband experience in high-demand areas. This is accomplished with the use of wider-spectrum bandwidths, Orthogonal Frequency-Division Multiple Access (OFDMA) and SC-FDMA (i.e., single carrier) air interfaces, and advanced antenna techniques. These techniques enable high spectral efficiency and an excellent user experience for a wide range of converged IP services. UMTS operators are rapidly adopting and offering IP services such as rich multimedia (e.g., video-on-demand, music download, video sharing), VoIP, PTT and broadband access to laptops and PDAs. Operators offer these services through access networks such as HSPA, HSPA+ and LTE.
In LTE as described in 3GPP TS 36.300 technical specification for EU-TRAN, one serving evolved base node (eNB) communicates via an uplink (UL) and downlink (DL) channel with user equipment (UE), thereby providing legacy interoperability by not depending upon dual mode communications. Due to data traffic, channel characteristics, or mobility of UE, a need frequently arises for a particular UE to be handed over from a source eNB to a target eNB. A handover (HO) procedure for a wireless communication system supports handover. As implemented, a degree of simplicity and economy in use of Over-the-Air (OTA) resources was sought by having the Radio Link Control (RLC) reset. However, for whatever OTA resources are preserved by not transferring RLC context, to achieve lossless user data during handover, context has to be transferred for a higher Packet Data Convergence Protocol (PDCP) layer, which performs header compression and ciphering on IP packets. In particular, in order to resend a small amount of data segmented by the RLC layer that is lost on either the UL or DL during RLC reset, a complete (larger) PDCP PDU has to be resent consuming OTA resources. In addition, PDCP layer performs PDCP PDU re-ordering during handover while RLC layer performs in-order delivery during other times, creating duplicating functionality between the two protocols. Further, upper layer functionality such as a TCP/IP transmission window collapse upon detection of packet loss. It should further be appreciated that during handover there is an interruption in UL user data since UE user data received on the UL by the target eNB cannot be routed to the Access Gateway (AGW) until a new S1 interface between the AGW and the target eNB is established.